The modern forestry industry is continually seeking to improve efficiency in processing timber. It is well-known to mount a timber-working device to a carrier vehicle in order to perform a number of operations in connection with timber processing. These operations may include one, or a combination of, grappling and felling a standing tree, delimbing a felled stem, debarking the stem, and cutting the stem into logs. Devices commonly known as harvester heads typically have the capability to perform all of these functions.
Many such harvester heads have the ability to measure the diameter and length of a log and automatically determine the optimal position of saw cuts in order to maximize the value of that log. Previously, an operator may have been required to calculate optimal value manually, or manually control the harvester head to perform cutting at points previously measured and marked. Automation of this process would be expected to improve productivity. However, elements of the process still currently require decision making on the part of the operator.
In particular, harvester heads commonly include two chainsaws—one at each end of the head. One of these chainsaws is typically designated as the “main” saw, having greater cutting capabilities in terms of stem diameter. The other chainsaw is usually used only for “topping” the stem—removing the undesirable end of the stem which is below a certain diameter—and as such the “top” saw generally has lower cutting capabilities than the main saw.
During typical operation of a harvester head—especially the processing of heavy limbed trees—a felled stem will be delimbed by feeding the stem through delimbing knives while logging the length and diameter of the stem. A cutting solution will then be determined based on the measured parameters.
Delimbing is generally performed from the largest diameter end of the stem—known as the Large End Diameter (LED)—in order to ensure that the harvester head may maintain a grip on the stem and allow the more valuable part of the stem to be processed. As such, the cutting solution is generally determined after the harvester head has arrived at the Small End Diameter (SED) of the stem.
Once a cutting solution has been determined the stem is usually reversed to the end of the stem with the LED, in order than the stem may be driven to the next cutting position, and the main saw used to cut the log. Following this method eliminates the need for the operator to make a decision regarding selection of the appropriate saw to make the first cut—reducing operator fatigue and maintaining operating efficiency. The process is continued to the last log length of the cutting solution, where the top saw is used to make the final cut.
This has several problems associated with it. In particular, the method requires the harvester to travel along the length of the stem three times—once for delimbing and measurement of the stem, once to return to the LED, and once to carry out the cutting solution. This adds to the fuel requirements of operating the head, and adds to the processing time—reducing the cost effectiveness of the harvester.
Further, it is generally desirable to reduce the number of passes a harvester head needs to make along the stem in order to reduce the damage to the stem by the feed mechanism—particularly for softer or ornamental wood where the value may decrease with bruising.
In some setups, the operator can choose whether to use the main or top saw to cut the stem at each position to achieve the cutting solution. This requires the operator to assess whether the diameter of the stem at a particular position is greater than the cutting capacity of the top saw, or whether the stem should be driven to the LED in order to process the stem as described above. This step takes time and causes operator stress and fatigue, which may in turn lead to poor decision making with regard to control of the harvester head and lost value to the forest owner.
All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinence of the cited documents. It will be clearly understood that, although a number of prior art publications are referred to herein, this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.
Throughout this specification, the word “comprise” or “include”, or variations thereof such as “comprises”, “includes”, “comprising”, or “including” will be understood to imply the inclusion of a stated element, integer or step, or group of elements integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.
Further aspects and advantages of the present disclosure will become apparent from the ensuing description which is given by way of example only.